1. Field of the Invention
The present invention relates to an ink ribbon cassette and, more particularly, to an ink ribbon cassette which houses an ink ribbon drawn from a cassette casing and taken up inside the casing through a recording section, and which is detachably mounted on a carriage of a recording apparatus.
2. Related Background Art
In order to align an ink ribbon cassette of this type in back-and-forth and left-and-right directions, two bosses are arranged on a carriage which mounts the ribbon cassette, a round hole is formed in the cassette at a position corresponding to one boss and an elongated hole is formed at a position corresponding to the other boss.
With this arrangement, however, the ink ribbon cassette must be mounted on the carriage so that the holes are immediately above the corresponding bosses. In order to prevent the cassette from being accidentally disengaged upward, the ink ribbon cassette must be fixed by a fixing means after the corresponding boss is engaged with the round hole. When the ink ribbon cassette is to be disengaged, the cassette must be pulled directly upward after the fixing means is released.
Since the casing of the ink ribbon cassette is fixed and the drawn ink ribbon is moved vertically, upper and lower positions of supply and take-up sections of the cassette must be defined so as not to be influenced by the vertical movement of the exposed ink ribbon. For this reason, slits, which are wide enough to allow smooth passage of the ink ribbon, are formed in the casing. However, since the slit width is small, the edge of the vertically moving ribbon abuts against the slit edge to be bent or to have ink removed therefrom. If the slit width is increased, the ribbon shifts widely in the vertical direction on the take-up side, resulting in irregular winding.
In order to prevent slackening of the ink ribbon at the supply side, a small tension force is applied to the ink ribbon. This tension member normally comprises a spring. However, since a normal spring has a small radius of curvature, when the ribbon receives a large tension force or receives a tension force for a long period of time, it may be bent or a printing operation may be interfered with.